Filtration is a widely used process in which a solid-liquid mixture, such as a slurry or sludge, is forced against a filtering media, with the solids retaining on the filtering media and the liquid phase passing through. The present invention relates more precisely to a vacuum box and a vacuum belt filter. Vacuum belt filters are conveyor-type filters widely used in the dewatering of slurries. The invention relates further to servicing a vacuum belt filter and to a method for liquid-solid separation of slurry in a belt filter. The invention relates further to a filter element. With vacuum is here understood a pressure below a surrounding pressure which typically, but not necessarily, is the atmospheric pressure of 1 bar.